Endoscope system and method of operating endoscope system

ABSTRACT

An endoscope system includes a light source unit and a processor. The processor is configured to calculate a compensation amount using a correction image having a biological information obtained by imaging the observation object using the green light, correct a correlation to be used in the biological information observation mode using the compensation amount, calculate, according to the corrected correlation, biological information based on an image obtained by imaging the observation object using the second blue light, and display a white light image which is obtained by imaging the observation object using the white light, on a display unit in the correction mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 15/993,599,filed May 31, 2018, which is a Continuation of PCT InternationalApplication No. PCT/JP2016/086341, filed on Dec. 7, 2016, which claimspriority under 35 U.S.C § 119(a) to Japanese Patent Application No.2015-250538, filed on Dec. 22, 2015. Each of the above application(s) ishereby expressly incorporated by reference, in its entirety, into thepresent application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an endoscope system that calculatesbiological information on an observation object, and a method ofoperating the endoscope system.

2. Description of the Related Art

In the medical field, it is general to perform diagnosis using endoscopesystems including a light source device, an endoscope, and a processordevice. Particularly, endoscope systems, which not only image anobservation object but also obtain observation images in which specifictissues or structures, such as blood vessels and duct structures, areenhanced, have become widespread. In such endoscope systems, forexample, the wavelength of illumination light to be radiated to theobservation object is studied, or estimation processing is performed onimages obtained by imaging the observation object. As a result, theobservation images in which the specific tissues and structures areenhanced are obtained.

Additionally, in recent years, there are also endoscope systems forobtaining biological information on the basis of images obtained byimaging the observation object. For example, diagnosis of a lesionlocation using the oxygen saturation (biological information) ofhemoglobin in blood is being performed. As a method of calculating theoxygen saturation, for example, as described in JP2013-022341A(JP5426620B), there is a method of acquiring image obtained by radiatinglight in a wavelength range where the light absorption coefficients ofoxygenated hemoglobin and reduced hemoglobin are different from eachother to an observation object, calculating predetermined arithmeticvalues using a plurality of images (hereinafter referred to as mainlycaptured images) include at least this image, and calculating oxygensaturation using a correlation in which the arithmetic values arematched with the oxygen saturation.

There is a case where the correlation between the arithmetic values andthe oxygen saturation as described above varies due to differences invarious parts, such as the esophagus, the stomach, or the largeintestine, or differences in patients, such as men and women or adultsand children. In contrast, in JP2013-022341A (JP5426620B), beforeactually observing the inside of the body using the oxygen saturation,the oxygen saturation of a normal part is calculated by imaging(hereinafter referred to as preliminary capturing) the normal part of apatient and a part and obtaining a plurality of images (hereinafterreferred to as preliminarily captured images). Then, a differencebetween the oxygen saturation of an actual normal part of the patientand the part and a reference value (for example, 70%) of the oxygensaturation of a general normal part in which the correlation isdetermined is calculated, and the correlation is compensated for on thebasis of the calculated difference. Accordingly, in JP2013-022341A(JP5426620B), the oxygen saturation is calculated so that the oxygensaturation can be accurately calculated irrespective of parts, patient'sindividual differences, or the like, and an observation mode(hereinafter referred to as an oxygen saturation observation mode) inwhich an image showing the value of the oxygen saturation is generatedand displayed is corrected.

In addition, there is known an endoscope system that in which a whitelight image obtained using white light and a special light imageobtained using special light, such as so-called narrowband light orfluorescence, are alternately acquired, and an attention region obtainedby processing the special light image is enhanced and displayed on thewhite light image (JP2011-104011A).

SUMMARY OF THE INVENTION

In order to obtain the plurality of mainly captured images to be usedfor the calculation of the oxygen saturation in the oxygen saturationobservation mode, it is necessary to change the wavelength or the likeof the illumination light to image the observation object two or moretimes. In a case where there is any movement in the observation objectbetween these kinds of imaging, the calculation accuracy of the oxygensaturation decreases due to the positional deviation of the observationobject between the respective mainly captured images. For this reason,basically, it is preferable that the mainly captured images arecontinuously acquired in a short period of time as much as possible soas to be regarded to be all substantially simultaneously obtained.

Since a plurality of preliminarily captured images are required also ina case where the oxygen saturation observation mode is corrected, theaccuracy of the correction decreases in a case where there is anymovement in the observation object while the plurality of preliminarilycaptured images are captured. For this reason, similarly to the mainlycaptured images, basically, it is preferable to obtain a plurality ofpreliminarily captured images while there is no movement of theobservation object. Particularly, in a case where the correction isinaccurate, the oxygen saturation that is calculated afterward becomesall inaccurate. Thus, it is more important to accurately correct theoxygen saturation observation mode accurately than keeping thecalculation accuracy of the oxygen saturation from decreasing.

In the case of JP2013-022341A (JP5426620B), by correcting the oxygensaturation observation mode, the oxygen saturation can be calculatedmore accurately than in an endoscope system that does not correct theoxygen saturation observation mode. However, JP2013-022341A (JP5426620B)does not mention correction accuracy. Additionally, in JP2011-104011A,the white light image and the special light image are alternatelyobtained. However, there is no oxygen saturation observation mode. Thus,although natural, JP2011-104011A also does not mention the correction ofthe oxygen saturation observation mode.

Additionally, in JP2013-022341A (JP5426620B), the oxygen saturation thatis one item of the biological information is observed. However, the sameapplies to a case where other biological information observation modesin which biological information other than the oxygen saturation iscalculated by using a plurality of mainly captured images. That is,similarly to the above, it is necessary to acquire the plurality ofpreliminarily captured images while there is no movement of theobservation object, to accurately correct the biological informationobservation mode.

An object of the invention is to provide an endoscope system capable ofcorrecting a biological information observation mode more reliably andaccurately than in the related art and a method of operating theendoscope system, in the endoscope system having the biologicalinformation observation mode and a correction mode that corrects thebiological information observation mode.

The endoscope system of the present inventing is an endoscope systemhaving a biological information observation mode in which biologicalinformation on an observation object is observed, and a correction modein which the biological information observation mode is corrected. Theendoscope system comprises a light source unit that emits correctionillumination light to be used for a correction in the correction modeand emits white light at least once; a compensation amount calculationunit that calculates a compensation amount of data to be used in thebiological information observation mode using correction images obtainedby imaging the observation object using the correction illuminationlight; a correction unit that corrects the biological informationobservation mode by compensating for the data using the compensationamount; and a display control unit that displays a white light image,which is obtained by imaging the observation object using the whitelight, on a display unit in the correction mode.

It is preferable that the biological information is an oxygen saturationof the observation object.

It is preferable that the endoscope system further comprises a regionsetting unit that sets a portion of each of the correction images to aregion to be used for the correction of the biological informationobservation mode, and the display control unit overlappingly displaysthe region set by the region setting unit on the white light image.

In the correction mode, it is preferable that the plurality ofcorrection images are acquired, and a plurality of the white lightimages are acquired.

It is preferable that the endoscope system further comprises a lightquantity ratio calculation unit that calculates a light quantity ratioof the plurality of white light images; and a light quantity ratiocompensation unit that compensates for a light quantity ratio of theplurality of correction images using the light quantity ratio calculatedby the light quantity ratio calculation unit.

It is preferable that the endoscope system further comprises a movementamount calculation unit that calculates a movement amount of theobservation object; and a positional deviation compensation unit thatcompensates a positional deviation of the plurality of correction imagesusing the movement amount.

It is preferable that the compensation amount calculation unitcalculates a plurality of the compensation amounts by using somecorrection images among the plurality of correction images and changinga combination of the correction images to be used, and the correctionunit compensates for the data to be used in the biological informationobservation mode using the plurality of compensation amounts or one ofthe plurality of compensation amounts.

It is preferable that the endoscope system further comprises a movementamount calculation unit that calculates a movement amount of theobservation object, and the correction unit compensates for the data tobe used in the biological information observation mode using a valueobtained by weighting and averaging the plurality of compensationamounts using the movement amount.

It is preferable that the endoscope system further comprises a movementamount calculation unit that calculates a movement amount of theobservation object, and the correction unit compensates for the data tobe used in the biological information observation mode using onecompensation amount selected from the plurality of compensation amountsusing the movement amount.

That is, it is preferable that the light source unit makes a lightemission interval of two correction illumination lights of a combinationthat most contributes to calculation accuracy of the compensation amountamong a plurality of the correction illumination lights shorter than alight emission interval of the other correction illumination lights.

The method of operating an endoscope system of the invention is a methodof operating an endoscope system having a biological informationobservation mode in which biological information on an observationobject is observed, and a correction mode in which the biologicalinformation observation mode is corrected. The method comprises a stepin which a light source unit emits correction illumination light to beused for a correction in the correction mode and emits white light atleast once; a step in which a compensation amount calculation unitcalculates a compensation amount of data to be used in the biologicalinformation observation mode using correction images obtained by imagingthe observation object using the correction illumination light; a stepin which a correction unit corrects the biological informationobservation mode by compensating for the data using the compensationamount; and a step in which a display control unit displays a whitelight image, which is obtained by imaging the observation object usingthe white light, on a display unit in the correction mode.

In the endoscope system and the method of operating an endoscope systemof the invention, in the correction mode, not only the correction imagesare acquired, but also the white light images are acquired anddisplayed. For this reason, a situation where the correction cannot beaccurately performed, such as a case where there is any movement in theobservation object or a case where a portion unsuitable for thecorrection is imaged, while the plurality of correction images areacquired, can be easily perceived, the correction images can beacquired, and the correction can be performed again. For this reason, inthe endoscope system and the method of operating the endoscope system ofthe invention, the biological information observation mode can becorrected more reliably and accurately than in the related art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of an endoscope system.

FIG. 2 is a block diagram of the endoscope system.

FIG. 3 is a light emission pattern in an oxygen saturation observationmode (biological information observation mode).

FIG. 4 is a light emission pattern in a correction mode.

FIG. 5 is a graph illustrating the spectral transmittance of a colorfilter.

FIG. 6 is a block diagram of a special processing unit.

FIG. 7 is a first feature space representing a correlation betweenarithmetic values and oxygen saturation.

FIG. 8 is a graph illustrating the light absorption coefficients ofoxygenated hemoglobin and reduced hemoglobin.

FIG. 9 is a graph illustrating the light absorption coefficient of ayellow coloring agent.

FIG. 10 is a second feature space to be used for calculation of acompensation amount.

FIG. 11 is a flowchart illustrating a flow of operation of the specialobservation mode.

FIG. 12 is a flowchart illustrating a flow of the operation of acorrection mode.

FIG. 13 is a flowchart illustrating a flow of the operation of theoxygen saturation observation mode (biological information observationmode).

FIG. 14 is a block diagram of a special processing unit of a secondembodiment.

FIG. 15 is a white light image in which a use region is overlappinglydisplayed.

FIG. 16 is a block diagram of a special processing unit of a thirdembodiment.

FIG. 17 is a block diagram of a special processing unit of a fourthembodiment.

FIG. 18 is a light emission pattern in a correction mode of a fifthembodiment.

FIG. 19 is a block diagram of a special processing unit of amodification example.

FIG. 20 is a block diagram of the special processing unit of themodification example.

FIG. 21 is a block diagram of the special processing unit and itsperiphery of the modification example.

FIG. 22 is a block diagram of the special processing unit of themodification example.

FIG. 23 is a light emission pattern in the correction mode.

FIG. 24 is a light emission pattern in the correction mode.

FIG. 25 is a block diagram of an endoscope system using a broadbandlight source and a rotation filter.

FIG. 26 is an explanatory view illustrating the configuration of therotation filter.

FIG. 27 is a schematic view of a capsule endoscope.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

As illustrated in FIG. 1, an endoscope system 10 has an endoscope 12, alight source device 14, a processor device 16, a monitor 18 that is adisplay unit, and a console 19. The endoscope 12 is optically connectedto the light source device 14 and is electrically connected to theprocessor device 16. The endoscope 12 has an insertion part 12 a to beinserted into a subject, an operating part 12 b provided at a base endportion of the insertion part 12 a, and a bending part 12 c and a distalend part 12 d provided on a distal end side of the insertion part 12 a.By operating an angle knob 12 e of the operating part 12 b, the bendingpart 12 c is bent. The distal end part 12 d is directed in a desireddirection as a result of the bending of the bending part 12 c. Inaddition, the distal end part 12 d is provided with a jet port (notillustrated) that jets air, water, or the like toward an observationobject.

Additionally, the operating part 12 b is provided with a mode changeoverswitch 13 a and a zooming operation part 13 b other than the angle knob12 e. The mode changeover switch 13 a is used for switching theoperation of observation modes. The endoscope system 10 has a normalobservation mode and a special observation mode. The normal observationmode is an observation mode in which a natural-tone image (hereinafter,referred to as a normal image) obtained by imaging the observationobject using white light for illumination light is displayed on themonitor 18.

The special observation mode includes a biological informationobservation mode and a correction mode. The biological informationobservation mode is an observation mode in which biological informationon the observation object is observed (the observation object isobserved in a state where at least the biological information can beobserved). The biological information is, for example, numericalinformation, such as oxygen saturation and the concentration of bloodvessels, image information, which is a result obtained by extractingsome tissue or the like from observable tissue or the like, such as “animage of blood vessels at a specific depth”, and the like. In thepresent embodiment, the biological information observation mode is anoxygen saturation observation mode in which the oxygen saturation of theobservation object is calculated. Therefore, in the oxygen saturationobservation mode, the oxygen saturation of the observation object iscalculated using a plurality of mainly captured images obtained byimaging the observation object, an image (hereinafter referred to as anoxygen saturation image) showing the values of the calculated oxygensaturation using pseudo-colors is generated, and the generated image isdisplayed on the monitor 18. The oxygen saturation image is an exampleof a biological information image, and a biological information imageregarding the biological information to be calculated is generated anddisplayed in a case where other biological information is calculated,extracted, and the like (hereinafter referred to as calculation and thelike) in the biological information observation mode.

The correction mode is a mode in which the biological informationobservation mode is corrected. The correction mode is automaticallyperformed before the biological information is calculated and the likeat least in the biological information observation mode. Additionally,in the correction mode, a normal part with no clear lesion or the likeis preliminarily captured, and a compensation amount of data to be usedfor the calculation and the like of the biological information usingpreliminarily captured images obtained in the preliminary capturing iscalculated. Then, by compensating for the data to be used for thecalculation and the like of the biological information using thecalculated compensation amount, the biological information observationmode is corrected.

That is, since the biological information observation mode is the oxygensaturation observation mode, the oxygen saturation observation mode iscorrected in the correction mode. That is, in the correction mode, acompensation amount ΔD of the data to be used for the calculation of theoxygen saturation in the oxygen saturation observation mode iscalculated using the preliminarily captured images. Then, the data to beused for the calculation of the oxygen saturation is compensated forusing the calculated compensation amount ΔD. The data to be used for thecalculation of the oxygen saturation is, for example, a correlation inwhich arithmetic values calculated using the plurality of mainlycaptured images, and the oxygen saturation are matched with each other.In addition, the correction mode can be executed at a certain timingduring the biological information observation mode by operation inputfrom the console 19 or the like. That is, during the execution of thebiological information observation mode, the correction mode can berandomly interrupted and executed as needed.

The processor device 16 is electrically connected to the monitor 18 andthe console 19. The monitor 18 outputs and displays the images in therespective observation modes, the image information accompanying theimages, and the like. The console 19 functions as a user interface thatreceives input operation, such as function setting. In addition, anexternal recording unit (not illustrated) that records the images, theimage information, and the like may be connected to the processor device16.

As illustrated in FIG. 2, the light source device 14 includes a lightsource unit 20 that emits the illumination light, and a light sourcecontrol unit 22 that controls driving of the light source unit 20.

The light source unit 20 includes four light sources of a BS lightsource 20 a, a BL light source 20 b, a G light source 20 c, and a Rlight source 20 d. In the present embodiment, the BS light source 20 a,the BL light source 20 b, the G light source 20 c, and the R lightsource 20 d are all light emitting diodes (LEDs). Instead of such LEDs,a combination of a laser diode (LD), a fluorescent body, and a bandlimiting filter, a combination of a lamp, such as a xenon lamp, and aband limiting filter, or the like can be used for the light source unit20.

The BS light source 20 a is a blue light source that emits first bluelight BS having a central wavelength of about 450±10 nm and having awavelength range of about 420 nm to 500 nm. The BL light source 20 b isa blue light source that emits blue, so-called narrowband light(hereinafter referred to as second blue light BL) having a centralwavelength and a wavelength range of about 470 nm±10 nm. The G lightsource 20 c is a green light source that emits green light G having acentral wavelength of about 540±20 nm and having a wavelength range ofabout 480 nm to 600 nm. The R light source 20 d is a red light sourcethat emits red light R having a central wavelength of about 640±20 nmand having a wavelength range of about 600 nm to 650 nm.

The light source control unit 22 independently controls the timing ofturning on/off the respective light sources 20 a to 20 d that constitutethe light source unit 20, the light emission amount thereof at the timeof the turn-on, and the like. Under the control of the light sourcecontrol unit 22, the light source unit 20 emits normal observationillumination light to be used in the normal observation mode, biologicalinformation observation illumination light to be used in the biologicalinformation observation mode of the special observation mode, andcorrection illumination light to be used in the correction mode. Thatis, since the biological information observation mode is the oxygensaturation observation mode, the biological information observationillumination light is oxygen saturation observation illumination light.

In the case of the normal observation mode, the light source controlunit 22 simultaneously turns on the BS light source 20 a, the G lightsource 20 c, and the R light source 20 d. For this reason, the normalobservation illumination light is white light including the first bluelight BS, the green light G, and the red light R. In the presentembodiment, in the case of the normal observation mode, the light sourceunit 20 always emits the above white light, but may emit the white lightin accordance with imaging timings (hereinafter referred to as imagingframes) of the observation object.

In the case of the oxygen saturation observation mode, the light sourcecontrol unit 22 alternately repeats turn-on or turn-off of therespective light sources 20 a to 20 d in a first pattern and a secondpattern. The first pattern is a light emission pattern in which the BLlight source 20 b is independently turned on. For this reason, in thecase of the first pattern, the second blue light BL becomes theillumination light. Meanwhile, the second pattern is a pattern in whichthe BS light source 20 a, the G light source 20 c, and the R lightsource 20 d are simultaneously turned on. For this reason, in the caseof the second pattern, the white light including the first blue lightBS, the green light G, and the red light R becomes the illuminationlight. Hence, in the oxygen saturation observation mode, as illustratedin FIG. 3, the second blue light BL and the white light are alternatelyand repeatedly emitted in accordance with the imaging frames.

A mainly captured image obtained by imaging the observation object usingthe second blue light BL that is the illumination light of the firstpattern, directly carries the most information on the oxygen saturationin a case where the observation object is irradiated. Meanwhile, amainly captured image obtained by imaging the observation object usingthe white light that is the illumination light of the second pattern, isused in order to more accurately calculate the information on the oxygensaturation carried by the second blue light BL. Hence, the oxygensaturation illumination light is the second blue light BL.

In the case of the correction mode, basically, the light source controlunit 22 independently and sequentially turns on the BS light source 20a, the BL light source 20 b, the G light source 20 c, and the R lightsource 20 d, respectively. Additionally, the light source control unit22 simultaneously turns on the BS light source 20 a, the G light source20 c, and the R light source 20 d at least once while, before, or afterthese respective light sources 20 a to 20 d are independently turned on,respectively. Hence, in the correction mode, the light source unit 20sequentially emits the first blue light BS, the second blue light BL,the green light G, and the red light R, and emits the white light atleast once during, before, or after emission of each of these colorlights. The first blue light BS, second blue light BL, the green lightG, and the red light R among such illumination lights are correctionillumination lights to be used for the correction of the oxygensaturation observation mode (biological information observation mode).The white light, which is emitted while, before, or after the correctionillumination light is emitted, is illumination light for obtaining awhite light image 202 (refer to FIG. 15) to be displayed on the monitor18 in a case where correction images are obtained using the correctionillumination light.

In the correction mode of the present embodiment, the correctionillumination lights are sequentially turned on in order of the firstblue light BS, the second blue light BL, the green light G, and the redlight R. Additionally, by certainly emitting the white light one timewhile each of these correction illumination lights in colors is turnedon, the light source unit 20 inserts emission of the white light two ormore times. Hence, in the correction mode of the present embodiment asillustrated in FIG. 4, the light source unit 20 emits the first bluelight BS, the white light, the second blue light BL, the white light,the green light G, the white light, and the red light R in this order inaccordance with the imaging frames. In a case where the correction modeis repeated, this light emission pattern is repeated.

The illumination light emitted from the light source unit 20 is incidenton a light guide 41. The light guide 41 is built in the endoscope 12 anda universal cord (a cord that connects the endoscope 12, and the lightsource device 14 and the processor device 16 to each other), andpropagates the illumination light to the distal end part 12 d of theendoscope 12. In addition, multimode fiber can be used as the lightguide 41. As an example, a fine-diameter fiber cable of which the corediameter is 105 μm, the clad diameter is 125 μm, and a diameterincluding a protective layer used as an outer cover is ϕ0.3 mm to 0.5 mmcan be used.

The distal end part 12 d of the endoscope 12 is provided with anillumination optical system 30 a and an imaging optical system 30 b. Theillumination optical system 30 a has an illumination lens 45, and theillumination light is radiated to the observation object via theillumination lens 45. The imaging optical system 30 b has an objectivelens 46, a zoom lens 47, and an image sensor 48. The image sensor 48images the observation object using reflected light or the like(including scattered light, fluorescence emitted from the observationobject, fluorescence due to medicine administered to the observationobject, or the like) of the illumination light returning from theobservation object via the objective lens 46 and the zoom lens 47. Inaddition, the zoom lens 47 is moved by operating the zooming operationpart 13 b, and magnifies or reduces the observation object to be imagedusing the image sensor 48.

The image sensor 48 is a color sensor of a primary color system, andincludes three types of pixels of a blue pixel (B pixel) having a blue(B) color filter, a green pixel (G pixel) having a green (G) colorfilter, and a red pixel (R pixel) having a red (R) color filter. Asillustrated in FIG. 5, a blue color filter allows mainly blue rangelight, specifically, light in a wavelength range of 380 to 560 nm to betransmitted therethrough. The transmittance of the blue color filterbecomes a peak in the vicinity of a wavelength of 460 to 470 nm. Thegreen color filter allows mainly green range light, specifically, lightin a wavelength range of 460 to 470 nm to be transmitted therethrough. Ared color filter allows mainly red range light, specifically, light in awavelength range of 580 to 760 nm to be transmitted therethrough.

In a case where the observation object is imaged using the image sensor48, three types of images of a B image (blue image) shot and obtained ina B pixel, a G image (green image) obtained by being imaged in a Gpixel, and an R image (red image) obtained being imaged in an R pixelcan be obtained to the maximum in one-time imaging. In the case of thenormal observation mode, since the normal observation illumination lightto be used is the white light, the Bc image, a Gc image, and an Rc imageare obtained as shown in Table 1. The Bc image is an image obtained byimaging the observation object, mainly using reflected light of thefirst blue light BS, and the like, included in the normal observationillumination light, and the Gc image is an image obtained by imaging theobservation object, mainly using reflected light of the green light G,and the like, included in the normal observation illumination light.Similarly, the Rc image is an image obtained by imaging the observationobject, mainly using reflected light of the red light R, and the like,included in the normal observation illumination light.

TABLE 1 Normal observation mode Illumination light White light Pixel tobe imaged B pixel G pixel R pixel Component of First blue Green Redcorresponding light BS light G light R illumination light Obtained imageBc image Gc image Rc image

Meanwhile, in the special observation mode of the present embodiment, inthe oxygen saturation observation mode that is the biologicalinformation observation mode, and the correction mode, the types andlight emission patterns of the illumination light are different fromeach other. Thus, images are different from each other in the respectivemodes. In the case of the oxygen saturation observation mode, theillumination light is alternately switched to the second blue light BL(oxygen saturation illumination light) and the white light in accordancewith the imaging frames. For this reason, as shown in Table 2, a B1image, a G1 image, and an R1 image are acquired using the second bluelight BL, and a B2 image, a G2 image, and an R2 image are obtained usingthe white light. The B1 image is an image obtained by imaging theobservation object in the B pixel using reflected light of the secondblue light BL, and the like. Similarly, the G1 image is an imageobtained by imaging the observation object in the G pixel using thereflected light of the second blue light BL, and the like, and the R1image is an image obtained by imaging the observation object in the Rpixel using the reflected light of the second blue light BL, and thelike. However, the reflected light of the second blue light BL is hardlytransmitted through the green color filter of the G pixel and the redcolor filter of the R pixel. Thus, in a case where fluorescence or thelike is not generated from the observation object, in an imaging framein which the second blue light BL is used for the illumination light, animage that is substantially obtained is only the B1 image. Additionally,although the same images as those of the normal observation mode areobtained in imaging frames in which the white light is used for theillumination light, respective images obtained in the imaging frames inwhich the white light is used for the illumination light in the oxygensaturation observation mode are referred to as the B2 image, the G2image, and the R2 image for the purpose of distinction. In addition, theB1 image, the G1 image, the R1 image, the B2 image, the G2 image, andthe R2 image acquired in the oxygen saturation observation mode aremainly captured images.

TABLE 2 Oxygen saturation observation mode (Biological informationobservation mode) Illumination light Second blue light BL White lightPixel to be B pixel G pixel R Pixel B pixel G pixel R Pixel imagedComponent of Second blue (Second blue (Second blue First blue Greenlight G Red light R Corresponding light BL light BL) light BL) light BSIllumination light Obtained image B1 image (G1 image) (R1 image) B2image G2 image R2 image

In the case of the correction mode, the illumination light is switchedin order of the first blue light BS, the second blue light BL, the greenlight G, and the red light R in accordance with the imaging frames, andthe imaging frames in which the white light is used for the illuminationlight are inserted therebetween. As shown in Table 3, in an imagingframe in which the first blue light BS is used for the illuminationlight, a Bp image, a Gp image, and an Rp image are obtained. The Bpimage is an image obtained by imaging the observation object in the Bimage using the reflected light of the first blue light BS, and thelike. Similarly, the Gp image is an image obtained by imaging theobservation object in the G image using the reflected light of the firstblue light, and the like, and the Rp image is an image obtained byimaging the observation object in the R image using the reflected lightof the first blue light, and the like. However, the reflected light ofthe first blue light BS is hardly transmitted through the green colorfilter of the G pixel and the red color filter of the R pixel. Thus, ina case where fluorescence or the like is not generated from theobservation object, in an imaging frame in which the first blue light BSis used for the illumination light, an image that is substantiallyobtained is only the Bp image.

Additionally, in an imaging frame in which the second blue light BL isused for the illumination light, a Bq image, a Gq image, and an Rq imageare obtained. The Bq image is an image obtained by imaging theobservation object in the B image using the reflected light of thesecond blue light BL, and the like. Similarly, the Gq image is an imageobtained by imaging the observation object in the G image using thereflected light of the second blue light BL, and the like, and the Rqimage is an image obtained by imaging the observation object in the Rimage using the reflected light of the second blue light BL, and thelike. However, the reflected light of the second blue light BL is hardlytransmitted through the green color filter of the G pixel and the redcolor filter of the R pixel. Thus, in a case where fluorescence or thelike is not generated from the observation object, in an imaging framein which the second blue light BL is used for the illumination light, animage that is substantially obtained is only the Bq image.

TABLE 3 Correction mode Illumination light First blue light BS Secondblue light BL Pixel to be B pixel G pixel R pixel . . . B pixel G pixelR pixel . . . imaged Component of First blue (First blue (First blue . .. Second blue (Second blue (Second blue . . . corresponding light BSlight BS) light BS) light BL light BL) light BL) illumination lightObtained Bp image (Gp image) (Rp image) . . . Bq image (Gq image) (Rqimage) . . . image

As shown in Table 4, in the correction mode, a Br image, a Gr image, andan Rr image are obtained in an imaging frame in which the green light Gis used for the illumination light. The Gr image is an image obtained byimaging the observation object in the G pixel using the reflected lightof the green light G, and the like. Similarly, the Br image is an imageobtained by imaging the observation object in the B pixel using thereflected light of the green light G, and the like, and the Rr image isan image obtained by imaging the observation object in the R pixel usingthe reflected light of the green light G, and the like. However, thegreen light G is hardly transmitted through the blue color filter of theB pixel and the red color filter of the R pixel. Thus, in a case wherefluorescence or the like is not generated from the observation object,an image that is substantially obtained is only the Gr image in theimaging frame in which the green light G is used for the illuminationlight.

Additionally, in the correction mode, a Bs image, a Gs image, and an Rsimage are obtained in an imaging frame in which the red light R is usedfor the illumination light. The Rs image is an image obtained by imagingthe observation object in the R pixel using the reflected light of thered light R, and the like. Similarly, the Bs image is an image obtainedby imaging the observation object in the B pixel using the reflectedlight of the red light R, and the like, and the Gs image is an imageobtained by imaging the observation object in the G pixel using thereflected light of the red light R, and the like. However, the red lightR is hardly transmitted through the blue color filter of the B pixel,and the green color filter of the G pixel. Thus, in a case wherefluorescence or the like is not generated from the observation object,an image that is substantially obtained is only the Rs image in theimaging frame in which the red light R is used for the illuminationlight.

TABLE 4 Correction mode Illumination light . . . Green light G . . . Redlight R Pixel to be . . . B pixel G pixel R pixel . . . B pixel G pixelR pixel imaged Component of . . . (Green Green (Green . . . (Red light(Red light Red light corresponding light G) light G light G) R) R) Rillumination light Obtained . . . (Br image) Gr image (Rr image) . . .(Bs image) (Gs image) Rs image image

Additionally, as shown in Table 5, in the imaging frames in which thewhite light is used for the illumination light in the correction mode, aBt image, a Gt image, and an Rt image are obtained. The Bt image is animage obtained by imaging the observation object in the B pixel, mainlyusing the reflected light of the first blue light BS, and the like,included in the white light. Similarly, the Gt image is an imageobtained by imaging the observation object in the G pixel, mainly usingthe reflected light of the green light G, and the like, included in thewhite light, and the Rt image is an image obtained by imaging theobservation object in the R pixel, mainly using the reflected light ofthe red light R, and the like, included in the white light. Hence,although these images are the same as the Bc image, the Gc image, andthe Rc image obtained in the normal observation mode, these images arereferred to as the Bt image, the Gt image, and the Rt image,respectively, for the purpose of distinction. In addition, the Bp image,the Gp image, the Rp image, the Bq image, the Gq image, the Rq image,the Bs image, the Gs image, the Rs image, the Bt image, the Gt image,and the Rt image acquired in the correction mode are the preliminarilycaptured images. Additionally, the Bp image, the Bq image, the Gr image,and the Rs image among these images are correction images to be actuallyused for the correction of the oxygen saturation observation mode.

TABLE 5 Correction mode Illumination light . . . White light . . . Pixelto be imaged . . . B pixel . . . R pixel Component of . . . First blue .. . Red corresponding light BS light R illumination light Obtained image. . . Bt image . . . Rt image

In addition, as the image sensor 48, a charge coupled device (CCD) imagesensor or a complementary metal-oxide semiconductor (CMOS) image sensoris available. Additionally, although the image sensor 48 of the presentembodiment is a color sensor of a primary color system, a color sensorof a complementary color system can also be used. The color sensor ofthe complementary color system has, for example, a cyan pixel providedwith a cyan color filter, a magenta pixel provided with a magenta colorfilter, a yellow pixel provided with a yellow color filter, and a greenpixel provided with a green color filter. Images obtained from the aboverespective pixels in colors in a case where the color sensor of thecomplementary color system is used can be converted into the B image,the G image, and the R image in a case where complementary color-primarycolor conversion is performed. Additionally, instead of the colorsensor, a monochrome sensor that is not provided with the color filtersmay be used as the image sensor 48. In this case, the above respectivecolor images can be obtained by sequentially imaging the observationobject using the respective illumination lights in colors, such as BGR.

The processor device 16 has a control unit 52, an image acquisition unit54, an image processing unit 61, and a display control unit 66.

The control unit 52 switches between the observation modes by receivinginput of a mode switching signal from the mode changeover switch 13 a,and inputting control signals to the light source control unit 22 andthe image sensor 48. Additionally, in the special observation mode,switching is made between the oxygen saturation observation mode and thecorrection mode. In addition, the control unit 52 also synchronouslycontrols the radiation timing of the illumination light, the timing ofthe imaging, and the like.

The image acquisition unit 54 acquires an image of the observationobject from the image sensor 48. In the case of the normal observationmode, the image acquisition unit 54 acquires the Bc image, the Gc image,and the Rc image for each imaging frame. In the case of the specialobservation mode of the present embodiment, in the oxygen saturationobservation mode (biological information observation mode), the imageacquisition unit 54 acquires the B1 image, the G1 image, and the R1image in the imaging frame in which the second blue light BL is used forthe illumination light, and acquires the B2 image, the G2 image, and theR2 image in the imaging frames in which the white light is used for theillumination light. Meanwhile, in the correction mode, the imageacquisition unit 54 acquires the Bp image, the Gp image, and the Rpimage in the imaging frame in which the first blue light BS is used forthe illumination light, acquires the Bq image, the Gq image and the Rqimage in the imaging frame in which the second blue light BL is used forthe illumination light, acquires the Br image, the Gr image, and the Rrimage in the imaging frame in which the green light G is used for theillumination light, and acquires the Bs image, the Gs image, and the Rsimage in the imaging frame in which the red light R is used for theillumination light. Moreover, in the imaging frames which are insertedbetween the above frames and in which the white light is used for theillumination light, the Bt image, the Gt image, and the Rt image areacquired.

Additionally, the image acquisition unit 54 has a digital signalprocessor (DSP) 56, a noise reduction unit 58, and a converting unit 59,and performs various kinds of processing on an acquired image usingthese units.

The DSP 56 performs various kinds of processing, such as defectcorrection processing, offset processing, gain correction processing,linear matrix processing, gamma conversion processing, demosaicingprocessing, and YC conversion processing, on the acquired image, asneeded.

The defect correction processing is the processing of compensating forthe pixel value of a pixel corresponding to a defective pixel of theimage sensor 48. The offset processing is the processing of reducing adark current component from the image subjected to the defect correctionprocessing, and setting an accurate zero level. The gain correctionprocessing is the processing of adjusting a signal level of each imageby multiplying the image subjected to the offset processing by a gain.The linear matrix processing is the processing of enhancing colorreproducibility on the image subjected to the offset processing, and thegamma conversion processing is the processing of adjusting thebrightness or saturation of the image after the linear matrixprocessing. The demosaicing processing (also referred to as equalizationprocessing or synchronization processing) is the processing ofinterpolating the pixel value of a missing pixel, and is performed onthe image after the gamma conversion processing. The missing pixel is apixel with no pixel value because pixels in other colors are disposed inthe image sensor 48 due to the arrangement of color filters. Forexample, since the B image is an image obtained by imaging theobservation object in the B pixel, there is no pixel value in pixels atpositions corresponding to the G pixel and the R pixel of the imagesensor 48. In the demosaicing processing, the pixel values of the pixelsat the positions of the G pixel and the R pixel of the image sensor 48are generated by interpolating the B image. The YC conversion processingis the processing of converting the image after the demosaic processinginto a luminance channel Y, a color difference channel Cb, and a colordifference channel Cr.

The noise reduction unit 58 performs noise reduction processing using,for example, a moving average method, a median filter method, or thelike, on the luminance channel Y, the color difference channel Cb, andthe color difference channel Cr. The converting unit 59 re-converts theluminance channel Y, the color difference channel Cb, and the colordifference channel Cr after the noise reduction processing into imagesin respective colors of BGR.

The image processing unit 61 has a normal processing unit 62 and aspecial processing unit 63. The normal processing unit 62 operates inthe normal observation mode, and performs color conversion processing,color enhancement processing, and structure enhancement processing onthe Bc image, the Gc image, and the Rc image, equivalent to one imagingframe, subjected to the above various kinds of processing to generate anormal image. In the color conversion processing, 3×3 matrix processing,gradation transformation processing, three-dimensional look-up table(LUT) processing, and the like are performed on the images in therespective colors of BGR. The color enhancement processing is theprocessing of enhancing the colors of an image, and the structureenhancement processing is the processing of enhancing, for example, thetissue or structure of the observation object, such as blood vessels orpit patterns. The display control unit 66 sequentially acquires normalimages from the normal processing unit 62, converts the acquired normalimages into a format suitable for display, and sequentially outputs anddisplays the converted images to and on the monitor 18. Accordingly, inthe case of the normal observation mode, a doctor or the like canobserve the observation object using a motion picture of the normalimages.

As illustrated in FIG. 6, the special processing unit 63 includes anarithmetic value calculation unit 70, a data storage unit 71, abiological information calculation unit 72, an image generation unit 73,a correction information calculation unit 75, a compensation amountcalculation unit 76, and a correction unit 77. The arithmetic valuecalculation unit 70, the biological information calculation unit 72, andthe image generation unit 73 among these units function in the oxygensaturation observation mode.

The arithmetic value calculation unit 70 acquires mainly captured imagesobtained in the biological information observation mode from the imageacquisition unit 54, and calculates arithmetic values that thebiological information calculation unit 72 uses for the calculation ofthe biological information using the mainly captured images. That is,since the biological information observation mode is the oxygensaturation observation mode in which the oxygen saturation is calculatedas the biological information, the arithmetic value calculation unit 70acquires the mainly captured images obtained in the oxygen saturationobservation mode from the image acquisition unit 54, and calculatesarithmetic values that the biological information calculation unit 72uses for the calculation of the oxygen saturation using the mainlycaptured images. More specifically, the arithmetic value calculationunit 70 acquires the B1 image, the B2 image, the G2 image, and the R2image from the image acquisition unit 54 in the oxygen saturationobservation mode. Then, a ratio B1/G2 of the B1 image to the G2 imageand a ratio R2/G2 of the R2 image to the G2 image are calculated foreach pixel, respectively. The ratio B1/G2 and the ratio R2/G2 arearithmetic values used for the calculation of the oxygen saturation.

The data storage unit 71 stores data to be used in a case where thebiological information calculation unit 72 calculates the biologicalinformation using the above arithmetic values calculated by thearithmetic value calculation unit 70. That is, since the oxygensaturation is calculated as the biological information, the data storageunit 71 stores a correlation between the above arithmetic valuescalculated by the arithmetic value calculation unit 70 and the oxygensaturation in the form of an LUT or the like. As illustrated in FIG. 7,in a case where this correlation is expressed in a first feature spaceformed using a vertical axis Log (B1/G2) and a horizontal axis Log(R2/G2), isoplethic lines obtained by connecting points with oxygensaturation values together are formed substantially in a lateraldirection. Additionally, the isoplethic lines are located closer to alower side in a vertical axis direction as the oxygen saturation becomeslarger. For example, an isoplethic line 83 having an oxygen saturationof 100% is located below an isoplethic line 84 having an oxygensaturation of 0%.

The above correlation is closely correlated with light-absorptioncharacteristics of oxygenated hemoglobin (graph 86) and reducedhemoglobin (graph 87) that are illustrated in FIG. 8. Specifically, inthe wavelength (about 470±10 nm) of the second blue light BL, thedifference between the light absorption coefficients of the oxygenatedhemoglobin and the reduced hemoglobin is large. Thus, light absorptionamount varies due to the oxygen saturation of hemoglobin. For thisreason, in the second blue light BL, it is easy to handle information onthe oxygen saturation. Hence, the oxygen saturation can be calculated ina case where the ratio B1/G2 obtained by standardizing the B1 imageusing the G2 image for compensation of illuminance unevenness or thelike, is used. However, the ratio B1/G2 depends on not only the oxygensaturation but also the amount of blood. Thus, by using the ratio R2/G2that varies mainly depending on the amount of blood in addition to theratio B1/G2, the oxygen saturation can be calculated without beinginfluenced by the amount of blood. In addition, the wavelength (about540±20 nm) of the green light G included in the G2 image is a wavelengthwhere the light absorption coefficient is apt to vary due to the amountof blood because the light absorption coefficient of hemoglobin isrelatively high.

In addition, the positions and the shapes of the isoplethic lines in theabove first feature space are obtained in advance as a result ofperforming physical simulation of light scattering. Additionally,although the data storage unit 71 stores the correlations between theratio B1/G2 and the ratio R2/G2, and the oxygen saturation, the datastorage unit 71 may store other correlations. For example, in a casewhere the oxygen saturation is calculated using arithmetic values(hereinafter referred to as other arithmetic values) obtained as aresult of performing other calculation (for example, differenceprocessing) different from the above description based on the B1 image,the B2 image, the G2 image, and the R2 image, the data storage unit 71may store the correlation in which the other arithmetic values arematched with the oxygen saturation.

The biological information calculation unit 72 refers to the data storedin the data storage unit 71, and calculates and the like the biologicalinformation using the arithmetic values calculated by the arithmeticvalue calculation unit 70. In the present embodiment, the biologicalinformation calculation unit 72 functions as an oxygen saturationcalculation unit. Specifically, the biological information calculationunit 72 refers to the correlation stored in the data storage unit 71,and calculates an oxygen saturation corresponding to the ratio B1/G2 andthe ratio R2/G2 for each pixel. For example, an oxygen saturationcorresponding to a ratio B1*/G2* and a ratio R2*/G2* of a specific pixelis “40%” in a case where the correlation stored in the data storage unit71 is referred to. Hence, the biological information calculation unit 72calculates the oxygen saturation of this specific pixel to be “40%”.

In addition, the ratio B1/G2 and R2/G2 hardly become extremely large orextremely small. That is, the combination of the respective values ofthe ratios B1/G2 and the ratio R2/G2 is hardly distributed below theisoplethic line 83 (refer to FIG. 7) of an upper limit that is an oxygensaturation of 100% or conversely, the combination is hardly distributedabove the isoplethic line 84 (refer to FIG. 7) of a lower limit that isan oxygen saturation of 0%. In a case where the combination of therespective values of the ratio B1/G2 and the ratio R2/G2 is distributedbelow from the maximum isoplethic line 83, the biological informationcalculation unit 72 calculates the oxygen saturation of the pixel to be100%. Similarly, in a case where the combination of the respectivevalues of the ratio B1/G2 and the ratio R2/G2 is distributed above theisoplethic line 84 of the lower limit, the biological informationcalculation unit 72 calculates the oxygen saturation of the pixel to be0%. Additionally, in a case where a point corresponding to the ratioB1/G2 and the ratio R2/G2 is not distributed between the isoplethic line83 of the upper limit and the isoplethic line 84 of the lower limit, adisplay may be performed such that the reliability of the oxygensaturation in the pixel is low, and the oxygen saturation may not becalculated.

In the case of the biological information observation mode, the imagegeneration unit 73 generates a biological information image showing thebiological information calculated by the biological informationcalculation unit 72. That is, the image generation unit 73 generates theoxygen saturation image obtained by turning the oxygen saturation intoan image using the oxygen saturation calculated in the biologicalinformation calculation unit 72. Specifically, the image generation unit73 acquires the B2 image, the G2 image, and the R2 image, and gives again according to the oxygen saturation to these images for each pixel.For example, the image generation unit 73 multiplies all the B2 image,the G2 image, and the R2 image by the same gain “1” in pixels with anoxygen saturation of 60% or more. In contrast, in pixels with an oxygensaturation of less than 60%, the B2 image is multiplied by a gain ofless than “1”, and the G2 image and the R2 image are multiplied by again of “1” or more. Thereafter, the image generation unit 73 generatesan oxygen saturation image in color using the B2 image, the G2 image,and the R2 image to which the gain is given as described above. Oxygensaturation images generated by the image generation unit 73 are acquiredby the display control unit 66, and are sequentially displayed on themonitor 18.

In each oxygen saturation image generated by the image generation unit73, a high-oxygen region (in the present embodiment, a region where theoxygen saturation is 60 or more and 100% or less) is expressed innatural colors, similar to the normal image. On the other hand, alow-oxygen region where the oxygen saturation is less than a specificvalue (in the present embodiment, a region where the oxygen saturationis 0 or more and 60% or less) is expressed in colors (pseudo-colors)different from the normal image. In addition, in the present embodiment,in the case of the oxygen saturation observation mode, the imagegeneration unit 73 multiplies the low-oxygen region only by a gain forpseudo-coloring. However, the gain according to the oxygen saturationmay also be given to the high-oxygen region, and the overall oxygensaturation image may be pseudo-colored. Additionally, although thelow-oxygen region and the high-oxygen region are divided with an oxygensaturation of 60% as a boundary, any boundary may also be adopted.

Meanwhile, in the correction mode, the correction informationcalculation unit 75, the compensation amount calculation unit 76, thecorrection unit 77, and the image generation unit 73 among therespective units of the special processing unit 63 function.

The correction information calculation unit 75 acquires thepreliminarily captured images from the image acquisition unit 54, andcalculates biological information to be used for correction (hereinafterreferred to correction information) in the biological informationobservation mode using the preliminarily captured images. The correctioninformation is, for example, biological information peculiar to theobservation object representing the part, state, and the like of theobservation object. Specifically, the correction information calculationunit 75 first acquires at least the Bp image, the Bq image, the Grimage, and the Rs image from the image acquisition unit 54. Then,biological information relating to a yellow coloring agent (bilirubin,stercobilin, or the like) adhering to the observation object and havinglow dependability on the oxygen saturation, and the other biologicalinformation to be used for the correction of the oxygen saturationobservation mode are calculated. The expression “relating to a yellowcoloring agent” means that there is a correlation with the adhesionamount or concentration of the yellow coloring agent. The expression“having low dependability on the oxygen saturation” means that the valueof the yellow coloring agent information does not vary substantially dueto the value of the oxygen saturation.

More specifically, the correction information calculation unit 75 firstcalculates a ratio Bp/Gr of the Bp image to the Gr image, a ratio Bq/Grof to the Bq image to the Gr image, and a ratio Rs/Gr of the Rs image tothe Gr image for each pixel.

The Bp image is an image corresponding to the first blue light BS, andthe wavelength range (a central wavelength of about 450±10 nm) of thefirst blue light BS is an equal absorption wavelength in which the lightabsorption coefficient of hemoglobin is relatively high and the lightabsorption coefficients of the oxygenated hemoglobin and the reducedhemoglobin are approximately equal to each other (refer to FIG. 8). Forthis reason, the Bp image is an image of which the values are not apt tovary due to the oxygen saturation. Additionally, since the first bluelight BS has a wavelength range where the light absorption coefficientof the yellow coloring agent is approximately the highest as illustratedin FIG. 9, the light absorption amount is apt to vary in accordance withthe adhesion amount or concentration of the yellow coloring agent. Fromthese facts, the value of the ratio Bp/Gr obtained by standardizing theBp image using the Gr image for the compensation of the illuminanceunevenness or the like, hardly varies due to the oxygen saturation butvaries due to the adhesion amount or concentration of the yellowcoloring agent. In addition, since the wavelength range of the greenlight G corresponding to the Gr image is a wavelength range where thelight absorption amount is apt to vary due to the amount of blood, theratio Bp/Gr varies due to the amount of blood.

Additionally, the Bq image is an image corresponding to the second bluelight BL, and the wavelength range (about 470±10 nm) of the second bluelight BL is the wavelength range in which the light absorptioncoefficient of hemoglobin is relatively high and the light absorptioncoefficients of the oxygenated hemoglobin and the reduced hemoglobin aredifferent from each other (refer to FIG. 8). For this reason, the Bqimage is an image that is apt to vary due to the oxygen saturation.Additionally, the wavelength range of the second blue light BL isslightly shifted from the absorption peak of the yellow coloring agent,but has a large light absorption coefficient compared to otherwavelength ranges (refer to FIG. 9). From these facts, the value of theratio Bp/Gr obtained by standardizing the Bq image using the Gr imagefor the compensation of the illuminance unevenness or the like, variesdue to the oxygen saturation, and the adhesion amount or concentrationof the yellow coloring agent. Additionally, since the Gr image hasdependability on the amount of blood, the value of the ratio Bq/Grvaries due to the amount of blood.

Meanwhile, the Rs image is an image corresponding to the red light R,and the wavelength range (a central wavelength of about 640±20 nm) ofthe red light R is a wavelength range where the light absorptioncoefficient of hemoglobin is very small compared to the wavelength rangeof the first blue light BS or the second blue light BL (refer to FIG.8). For this reason, in the Rs image, there is a difference between thelight absorption coefficients of the oxygenated hemoglobin and thereduced hemoglobin. However, since the light absorption amount isexcessively small, there is substantially no dependability on the oxygensaturation. Additionally, also regarding the yellow coloring agent, thelight absorption coefficient of the yellow coloring agent in thewavelength range of the red light R is an extremely small value comparedto the wavelength range of the first blue light BS or the second bluelight B. Thus, the Rs image hardly varies due to the adhesion amount orconcentration of the yellow coloring agent. Hence, the value of theratio Rs/Gr obtained by standardizing the Rs image using the Gr imagefor the compensation of the illuminance unevenness or the like, hardlydepends on the oxygen saturation, or the adhesion amount orconcentration of the yellow coloring agent. However, the ratio Rs/Grvaries due to the amount of blood, reflecting the dependability of theGr image on the amount of blood.

From the above fact, at least the ratio Bp/Gr corresponds to biologicalinformation relating to the yellow coloring agent adhering to theobservation object and having low dependability on the oxygensaturation. However, in the present embodiment, the correctioninformation calculation unit 75 calculates biological information(hereinafter referred to as yellow coloring agent information) Vy whichis more accurately relating to the yellow coloring agent adhering to theobservation object and lower dependability on the oxygen saturation, onthe basis of following Equation A. The phase ϕ is a known amountadjusted in advance such that the yellow coloring agent information Vyobtained by the calculation based on Equation A become constant eventhough the oxygen saturation varies. The correction informationcalculation unit 75 inputs the yellow coloring agent information Vyafter the adjustment of the phase ϕ, and the ratio Rs/Gr, to thecompensation amount calculation unit 76 as the correction information.

Vy=(Bp/Gr)×cos ϕ+(Bq/Gr)×sin ϕ  [Equation A]

The compensation amount calculation unit 76 calculates the compensationamount of the data to be used for the calculation of the biologicalinformation from predetermined reference information, and the correctioninformation calculated by the correction information calculation unit75. That is, the compensation amount calculation unit 76 calculates thecompensation amount ΔD of the correlation used for the calculation ofthe oxygen saturation using the yellow coloring agent information Vy.Additionally, by using the correction information calculated by thecorrection information calculation unit 75, the compensation amountcalculation unit 76 substantially uses the correction images for thecalculation of the compensation amount. In the case of the presentembodiment, the reference information is the correlation between theyellow coloring agent information Vy acquired in a state where there isalmost no yellow coloring agent, and the ratio Rs/Gr. The yellowcoloring agent information Vy constituting the reference information isthe yellow coloring agent information Vy calculated in accordance withEquation A by adjusting the phase ϕ such that there is no changeresulting from the oxygen saturation using the Bp image, the Bq image,and the Gr image acquired in a state where there is substantially noyellow coloring agent. In this process, the phase ϕ of Equation A isalso determined. As the reference information, for example, a phantomobtained by imitating a living body can be determined in advance byimaging, simulation, or the like. In addition, the data to be used forthe calculation of the biological information in the biologicalinformation observation mode as above is the correlation stored in thedata storage unit 71 store in the present embodiment.

As illustrated in FIG. 10, the compensation amount calculation unit 76calculates the compensation amount ΔD using the second feature space inwhich the vertical axis is the yellow coloring agent information Vy, andthe horizontal axis is Log(Rs/Gr). Since the ratio Rs/Gr to be used forthe horizontal axis represents the amount of blood, the second featurespace represents the distribution of the yellow coloring agentinformation Vy with respect to the amount of blood, and a lineconnecting points where the yellow coloring agent information Vy isequal in the second feature space is an isoplethic line (hereinafterreferred to as an equal concentration line) in which the concentrations(or adhesion amounts) of the yellow coloring agent are equal to eachother.

The reference information forms a referential equal concentration line94 in the second feature space. For this reason, in a case where thereis actually no yellow coloring agent, points where the yellow coloringagent information Vy and the ratio Rs/Gr obtained by actually andpreliminarily capturing the observation object are determined within thesecond feature space lie on the referential equal concentration line 94.However, in a case where there is a yellow coloring agent, the pointslie on an equal concentration line 96 shifted from a referential equalconcentration line 94 due to the adhesion amount or concentration of theyellow coloring agent. Hence, in the second feature space, the equalconcentration line 96 on which the points represented by the yellowcoloring agent information Vy and the ratio Rs/Gr obtained by actuallypreliminarily capturing the observation object lie, the referentialequal concentration line 94, and a difference Δ in the vertical axisdirection represent the adhesion amount or concentration of the yellowcoloring agent. Hence, the compensation amount calculation unit 76calculates the compensation amount ΔD (=ΔZ×α) by calculating thedifference ΔZ between line the referential equal concentration line 94and the equal concentration line 96 and multiplying the difference by apredetermined coefficient α. In addition, the coefficient α is a valuefor scale-converting the difference ΔZ into a value suitable for thecompensation of the correlation stored in the data storage unit 71.Since the value of the yellow coloring agent information Vy becomeslarger as the adhesion amount or concentration of the yellow coloringagent is smaller, the equal concentration line of the second featurespace is formed below the referential equal concentration line 94.

The correction unit 77 corrects the biological information observationmode by compensating for the data to be used for the calculation and thelike of the biological information using the compensation amount ΔDcalculated by the compensation amount calculation unit 76. In thepresent embodiment, the correction unit 77 corrects the oxygensaturation observation mode by compensating for the correlation storedin the data storage unit 71 using the compensation amount ΔD.Specifically, the correction unit 77 adds the compensation amount ΔD tothe value of Log (B1/G2) of the vertical axis on all the isoplethiclines in the first feature space (refer to FIG. 7). That is, thecorrection unit 77 shifts all the isoplethic lines of the first featurespace upward on the vertical axis by the compensation amount ΔD. In thisway, an error factor (in the present embodiment, the adhesion amount orconcentration of the yellow coloring agent), such as a part or an actualstate, which is peculiar to an actual observation object, is reflectedin the first feature space compensated for by the correction unit 77.Hence, in the oxygen saturation observation mode, the biologicalinformation calculation unit 72 can calculate an accurate oxygensaturation that does not depend on the error factor peculiar to theobservation object by using the first feature space compensated for bythe correction unit 77.

As described above, while the biological information observation mode(oxygen saturation observation mode) is corrected using the correctioninformation calculation unit 75, the compensation amount calculationunit 76, and the correction unit 77, the image generation unit 73sequentially acquires the Bt image, the Gt image, and the Rt image (thatis, images obtained using the white light during the correction mode)from the image acquisition unit 54 in the correction mode. Then, theimage generation unit 73 performs the color conversion processing, thecolor enhancement processing, and the structure enhancement processingon the Bt image, the Gt image, and the Rt image equivalent to oneimaging frame, and generates the white light image 202. The white lightimage 202 is the same as the normal image of the normal observation modeexcept that the white light image is generated during the correctionmode. Hence, in a case where the white light image 202 is used, thenatural-tone observation object can be observed.

In the correction mode, the display control unit 66 sequentiallyacquires the above white light images 202 generated by the imagegeneration unit 73, and displays the acquired images on the monitor 18.For this reason, the observation of the observation object can becontinued without interruption using the white light image 202 or amotion picture including the white light images 202, in the midst ofcapturing the preliminarily captured images in the correction mode.

Next, a flow of a series of operation of the special observation modewill be described along a flowchart illustrated in FIGS. 11 to 13.First, in a case where the mode changeover switch 13 a is operated toswitch to the special observation mode as illustrated in FIG. 11 (S10),the control unit 52 executes the correction mode by inputting controlsignals to the light source control unit 22 and the image sensor 48(S11). In the correction mode, the oxygen saturation observation mode(biological information observation mode) is corrected by compensatingfor the correlation to be used for the calculation of the oxygensaturation using the preliminarily captured images obtained by thepreliminary capturing. Moreover, in the correction mode, while thepreliminarily captured images are obtained, the observation object isimaged using the white light, and the white light image 202 is displayedon the monitor 18. For this reason, the doctor or the like views thewhite light image 202 (or a motion picture including the white lightimages 202), and determines whether or not the correction the oxygensaturation observation mode has been accurately performed (S12).Specifically, since the correction of the oxygen saturation isaccurately performed in a case where the preliminary capturing isperformed under unsuitable conditions, it is checked that thepreliminary capturing has been appropriately performed while viewing thewhite light image 202 displayed on the monitor 18 during the correctionmode. For example, conditions regarding an imaging position, such aswhether or not there is any clear lesion in the observation object, andconditions regarding imaging situations, such as whether or the not thebrightness is suitable, or whether the observation object is not cleardue to movement of the observation object are determined from the whitelight image 202 obtained substantially simultaneously with thepreliminarily captured images.

In a case where it is determined from the white light image 202 thatthere is a possibility that the preliminary capturing is notappropriately performed and the biological information observation modeis not accurately corrected (S12: NO), the correction mode is againexecuted by an operation input from the console 19 or the like. On theother hand, in a case where it is determined from the white light image202 that the preliminary capturing is appropriately performed and thebiological information observation mode can be accurately corrected inaccordance with the observation object (S12: YES), the process proceedsto the oxygen saturation observation mode that is the biologicalinformation observation mode of the present embodiment by an operationinput from console 19 or the like (S13). In the oxygen saturationobservation mode, the endoscope system 10 calculates the oxygensaturation using the mainly captured images obtained by performing themain capturing, and displays the oxygen saturation image showing thevalues of the oxygen saturation using pseudo-colors, on the monitor 18.For this reason, the doctor or the like views and diagnoses the oxygensaturation image. In a case where diagnosing using the oxygen saturationimage, in a case where there is a doubt about shown values of the oxygensaturation, such as the values of the oxygen saturation are high as awhole or low as a whole and it is necessary to perform the correctionagain (S14), the process proceeds to the correction mode (S13) by anoperation input from the console 19 or the like, and the oxygensaturation observation mode is corrected again. Additionally, theendoscope system 10 repeatedly executes the oxygen saturationobservation mode by the operation of the mode changeover switch 13 auntil the oxygen saturation observation mode is ended (S15), andcontinuously displays oxygen saturation images on the monitor 18.

As illustrated in FIG. 12, in the correction mode (Step S11 of FIG. 11),first, the light source unit 20 emits the first blue light BS (S21),image sensor 48 automatically preliminarily captures the observationobject using the first blue light BS, and the image acquisition unit 54acquires the Bp image to be used for the correction of the oxygensaturation observation mode (S22). Next, the light source unit 20 emitsthe white light (S23). For this reason, in the next imaging frame inwhich the Bp image is obtained, the image sensor 48 automatically imagesthe observation object using the white light, and the image acquisitionunit 54 acquires the Bt image, the Gt image, and the Rt image (S24).Although in the middle of the preliminary capturing, the imagegeneration unit 73 generates a white light image 202 using the Bt image,the Gt image, and the Rt image obtained here, and the display controlunit 66 displays the white light image 202 on the monitor 18 (S25).

In an imaging frame next to the imaging frame in which the white lightimage 202 is obtained, the light source unit 20 emits the second bluelight BL (S26). Then, the image sensor 48 automatically images theobservation object using second blue light BL, and the image acquisitionunit 54 acquires the Bq image required for the correction of the oxygensaturation observation mode (S27). In the next imaging frame in whichthe Bq image is obtained, the light source unit 20 does not emit theillumination light for obtaining the next preliminarily captured imagesbut emits the white light again (S28). For this reason, the image sensor48 images the observation object using the white light, and the imageacquisition unit 54 acquires the Bt image, the Gt image, and the Rtimage again (S29). The image generation unit 73 generates a white lightimage 202 from the Bt image, the Gt image, and the Rt image, and thedisplay control unit 66 displays the generated white light image 202 onthe monitor 18 (S30).

In the next imaging frame, the light source unit 20 emits the greenlight G (S31). Then, the image sensor 48 automatically images theobservation object using the green light G, and the image acquisitionunit 54 acquires the Gr image required for the correction of the oxygensaturation observation mode (S32). Next, the light source unit 20 emitsthe white light again (S33), an image sensor 48 automatically images theobservation object using the white light, and the image acquisition unit54 acquires the Bt image, the Gt image, and the Rt image (S34). For thisreason, the image generation unit 73 generates a white light image 202using these images, and the display control unit 66 displays the whitelight image 202 on the monitor 18 (S35).

Then, in the next imaging frame, the light source unit 20 emits the redlight R (S36), the image sensor 48 automatically images the observationobject using the red light R, and the image acquisition unit 54 acquiresthe Rs image that is a final image required for the correction of theoxygen saturation observation mode (S37).

As described above, in a case where the plurality of preliminarilycaptured images (that is, the Bp image, the Bq image, the Gr image, andthe Rs image) required for the correction of the oxygen saturationobservation mode are acquired while generation and a display of thewhite light image 202 are inserted, the correction informationcalculation unit 75 calculates the biological information peculiar tothe observation object showing the part, state, and the like of theobservation object as the correction information using thesepreliminarily captured images (S38). In a case where the correctioninformation calculation unit 75 calculates the correction information,the compensation amount calculation unit 76 corrects the oxygensaturation observation mode by compensating for the correlation to beused for the calculation of the oxygen saturation using the correctioninformation calculated the correction information calculation unit 75(S40).

As illustrated in FIG. 13, in the oxygen saturation observation mode(Step S13 of FIG. 11), the light source unit 20 first emits the secondblue light BL (S51). The, then image sensor 48 automatically images theobservation object using the second blue light BL, and the imageacquisition unit 54 acquires the B1 image indispensable for thecalculation of the oxygen saturation (S52). Thereafter, in the nextimaging frame, the light source unit 20 emits the white light (S53), theimage sensor 48 automatically images the observation object using thewhite light, and thereby the image acquisition unit 54 acquires the B2image the G2 image, and the R2 image required for the calculation of theoxygen saturation and the generation of the oxygen saturation image(S54).

In a case where the B1 image, the B2 image, the G2 image, and the R2image are obtained in this way, the arithmetic value calculation unit 70calculates arithmetic values required for the calculation of the oxygensaturation (S55). Specifically, the arithmetic value calculation unit 70calculates the ratio B1/G2 and the ratio R2/G2, respectively, for eachpixel.

Then, the biological information calculation unit 72 refers to thecorrelation of the data storage unit 71, and calculates the oxygensaturation of the observation object for each pixel from the ratio B1/G2and the ratio R2/G2 calculated by the arithmetic value calculation unit70 (S56). Though natural, the biological information calculation unit 72does not use the default correlation stored in advance in the datastorage unit 71 but uses the correlation compensated for by thecorrection unit 77 in the correction mode. For this reason, since thereis no influence from the error factor peculiar to the observationobject, the oxygen saturation calculated by the biological informationcalculation unit 72 is accurate.

In a case where the biological information calculation unit 72calculates the oxygen saturation, the image generation unit 73 gives again according to the oxygen saturation to the B2 image, the G2 image,and the R2 image, and generates the oxygen saturation image representingthe values of the oxygen saturation using the pseudo-colors, and thedisplay control unit 66 displays the oxygen saturation image on themonitor 18 (S57).

As described above, the endoscope system 10 has the biologicalinformation observation mode, the correction mode in which thebiological information observation mode is corrected. In the correctionmode, the endoscope system 10 not only simply obtain the preliminarilycaptured images to correct the biological information observation mode,but also generates and displays the white light image 202 while (orbefore or after) the preliminarily captured images are obtained. Forthis reason, the doctor or the like can continue observing theobservation object even during the correction mode.

Moreover, since the white light image 202 to be displayed on the monitor18 during the correction mode is acquired substantially simultaneouslywith the preliminarily captured images, this white light imagerepresents the state of the observation object while, before, or afterthe preliminarily captured images are obtained. For this reason, thedoctor or the like obtains an opportunity to determine whether or notthe preliminary capturing has been appropriately performed or whether ornot the oxygen saturation observation mode that is the biologicalinformation observation mode has been accurately corrected, by thedisplay of the white light image 202 during the correction mode.

In a case where the oxygen saturation observation mode (biologicalinformation observation mode) is executed in a case where thepreliminary capturing fails in the correction mode that is automaticallyperformed at the time of switching to the special observation mode andthe correction is not accurate, it is natural that the oxygen saturationis inaccurate. Thus, the oxygen saturation image cannot be utilized fordiagnosis. In contrast, in the endoscope system 10, there is anopportunity to determine whether or not the correction has beenappropriately performed by displaying the white light image 202 duringthe correction mode. Thus, as needed, before the process proceeds to theoxygen saturation observation mode, the correction mode can be executedagain to reliably and accurately correct the oxygen saturationobservation mode. Hence, in the endoscope system 10, in a case wherethere is no change (for example, secretion of mucus, or the like) of theobservation object in which the correction is required again, the oxygensaturation can be reliably and accurately calculated in a case where theprocess has proceeded to the oxygen saturation observation mode.

In addition, in the above first embodiment, the compensation amountcalculation unit 76 calculates the compensation amount ΔD using thesecond feature space, but may also calculate the compensation amount ΔDby performing conversion processing, in which the matrix processing anda one-dimensional look-up table (1D-LUT) are combined with each other,on the Bp image, the Bq image, the Gr image, and the Rs image.

In the above first embodiment, the oxygen saturation observation mode iscorrected with respect to the adhesion amount or concentration of theyellow coloring agent. However, the oxygen saturation observation modemay be corrected with respect to states peculiar to other observationobjects. In this case, the correction information calculation unit 75may calculate biological information regarding a state or the likepeculiar to an observation object used as a correction target, the likeas the correction information, instead of the biological informationregarding the adhesion amount or concentration of the yellow coloringagent. The operation of the compensation amount calculation unit 76 andthe correction unit 77 is the same as that of the above firstembodiment.

In the correction mode of the above first embodiment, in order to obtainthe preliminarily captured images, all the white lights are emitted toobtain the white light images 202 while the first blue light BS, thesecond blue light BL, the green light G, and the red light R are emitted(refer to FIG. 4). However, any of the timings at which these whitelights are emitted can be omitted. Additionally, the white light may beemitted to obtain the white light image 202 before emission of the firstblue light BS, or the white light may be emitted to obtain the whitelight image 202 also after emission of the red light R. That is, duringthe correction mode, the white light may be emitted at least once togenerate and display the white light image 202.

In the correction mode of the above first embodiment, except for thewhite light image 202, the preliminarily captured images are acquired inorder of the Bp image, the Bq image, the Gr image, and the Rs image(refer to FIG. 12). However, any acquisition order of the preliminarilycaptured images may be adopted. For example, the preliminarily capturedimages may be acquired in order of the Rs image, the Bq image, the Bpimage, and the Gr image. However, in a case where there is deviation(movement) of the observation object in the Bp image and the Bq imageamong these preliminarily captured images, the correction accuracy ofthe oxygen saturation observation mode is particularly apt to decrease.For this reason, it is preferable that the Bp image and the Bq image arecontinuously acquired as much as possible. That is, it is preferablethat the light emission interval of two correction illumination lightsof a combination that most contributes to the calculation accuracy ofthe compensation amount ΔD to be used for the correction of the oxygensaturation observation mode among a plurality of correction illuminationlights can be made shorter than the light emission interval of the othercorrection illumination lights. It is needless to say that the Bp imageand the Bq image are continuously acquired thoroughly with respect tothe acquisition order of the preliminarily captured images, and animaging frame for generating and displaying the white light image 202may be inserted between the Bq image and the Bq image.

Second Embodiment

In the first embodiment, the biological information observation mode(oxygen saturation observation mode) are corrected using an entirepreliminarily captured image. However, the biological informationobservation mode may be corrected using only a portion of thepreliminarily captured image instead of the entire preliminarilycaptured image. In a case where the biological information observationmode is corrected using a portion of the preliminarily captured image inthis way, as illustrated in FIG. 14, the special processing unit 63 isprovided with a region setting unit 201 that operates in the correctionmode.

The region setting unit 201 acquires preliminarily captured images (thatis, the Bp image, the Bq image, the Gr image, and the Rs image), to beused for the correction of the oxygen saturation observation mode thatis the biological information observation mode, from the imageacquisition unit 54, and sets a portion of each of these preliminarilycaptured images to a region (hereinafter referred to as a use region)203 (refer to FIG. 15) to be used for the correction of the oxygensaturation observation mode. In a case where the region setting unit 201sets the use region 203 with respect to the preliminarily capturedimage, the correction information calculation unit 75 calculatescorrection information only on the use region 203 set by the regionsetting unit 201. Accordingly, since the compensation amount calculationunit 76 also calculates the compensation amount ΔD with respect to theuse region, only the use region 203 that is a portion of thepreliminarily captured image instead of the entire preliminarilycaptured image is used for the compensation (that is, the correction ofthe oxygen saturation observation mode) of the correlation performed bythe correction unit 77. In this way, in a case where the use region 203is set in a portion of the preliminarily captured image and the oxygensaturation observation mode is corrected using only the use region 203instead of the entire preliminarily captured image, the error factor ofthe correction can be reduced. Thus, the oxygen saturation observationmode can be more accurately corrected.

The region setting unit 201 detects, for example, portions that becomethe error factor of the correction, such as an excessively brightportion (a portion in which halation occur), an excessively dark portion(a portion that is crushed black due to shortage of the quantity oflight), and a portion to which residual substances or residual liquidadheres, from the preliminarily captured image, and sets regionsexcluding these portions to the use region 203. The region setting unit201 may also perform determination from the shape or the like of theobservation object, detect a normal part that can be said not to have alesion or the like, and set the detected normal part to the use region203. Additionally, the region setting unit 201 may set a regionexcluding a circumferential edge of an image in which the illuminanceunevenness occurs easily, and a certain range of an inner portion of theobservation object to the use region 203. In addition, the use region203 can also be manually set by an operation input from the console 19or the like.

As described above, in a case where the region setting unit 201 sets aportion of a preliminarily captured image to the use region 203 and usesonly the use region 203 for the correction of the oxygen saturationobservation mode, the image generation unit 73 acquires information onthe position and range of the use region 203 (hereinafter referred to aspositional information) set by the region setting unit 201, from theregion setting unit 201. For example, as illustrated in FIG. 15, in acase where the display control unit 66 displays the white light image202 on the monitor 18, the display control unit 66 overlappingly displaythe use region 203 set by the region setting unit 201 on the white lightimage 202 on the basis of the positional information.

In a case where the use region 203 is overlapping displayed on the whitelight image 202 in this way, which region has been used for thecorrection of the oxygen saturation observation mode can be visuallyrecognized. Hence, the doctor or the like can confirm whether or not theuse region 203 is unsuitable in addition to confirming whether or notthe use region 203 is in a state that may become an error factor, suchas the movement of the observation object using the white light image202, and can perform the correction of the oxygen saturation again in acase where the use region 203 set by the region setting unit 201 set isunsuitable.

In the above second embodiment, the region setting unit 201 detects andsets the use region 203 using the preliminarily captured image. Insteadof this, however, the region setting unit 201 may set the use region 203using the white light image 202.

In the above second embodiment, the use region 203 is overlappingdisplayed on the white light image 202. However, a numerical value ofthe compensation amount ΔD or an indicator showing the numerical valueof the compensation amount ΔD may be further overlappingly displayed onthe white light image 202. This is because specific numerical values ofthe compensation amount ΔD also become a determination material ofwhether or not the correction of the oxygen saturation observation modehas been accurately performed. For example, in a case where thecompensation amount ΔD is extremely large, there is a possibility thatthe state of the observation object is far from a normal state to such adegree that a lesion is spreading in an imaged entire location. Such anabnormality can be perceived in a case where the specific numericalvalues of the compensation amount ΔD are viewed. The overlap display ofthe numerical values of the compensation amount ΔD are effective also inthe case of the first embodiment.

Third Embodiment

In the first embodiment, in the correction mode, the light source unit20 inserts the emission of the white light two or more times whilesequentially emitting the correction illumination lights for obtainingpreliminarily captured images. Accordingly, the white light images 202are respectively generated and displayed on the monitor 18 from theimages obtained in the respective imaging frames in which the whitelight is emitted.

In this way, in the correction mode, in a case where the light sourceunit 20 inserts the emission of the white light two or more times whilesequentially emitting the correction illumination lights for obtainingthe preliminarily captured images, and obtains the plurality of whitelight image 202, as illustrated in FIG. 16, it is preferable that thespecial processing unit 63 is further provided with the movement amountcalculation unit 301 and a positional deviation compensation unit 302that operate in the correction mode.

The movement amount calculation unit 301 sequentially acquires the whitelight images 202 generated by the image generation unit 73, andcalculates the movement amount of the observation object from theplurality of acquired white light images 202. Specifically, throughmatching of two white light images 202 that are sequentially acquired,the movement amount calculation unit 301 detects a plurality of vectors(henceforth, movement vector) showing the movement of the observationobject between the white light images 202. Directions and sizes, such asthe movement, rotation, and deformation of the observation object arecalculated from these movement vectors. Directions and sizes, such asthe movement, rotation, and deformation of the observation object thatare calculated in this way are the movement amount.

The positional deviation compensation unit 302 compensates for thepositional deviation of the observation object of the correction imagesusing the movement amount calculated by the movement amount calculationunit 301. That is, the positional deviation compensation unit 302compensates for the positional deviation of the observation object ofthe Bp image, the Bq image, the Gr image, and the Rs image that are thecorrection images.

For example, in a case where a movement amount is calculated from thewhite light image 202 (the white light image 202 obtained in Step S25 ofFIG. 12) first obtained in the correction mode, and the white lightimage 202 (the white light image 202 obtained in Step S30 of FIG. 12)that is obtained next, this movement amount is approximately equal tothe movement amount of the observation object between Bp images, Bqimages, or Gr images that are acquired before and after the white lightimage 202 that is first obtained and the white light image 202 that isnext obtained. Similarly, in a case where a movement amount iscalculated from the white light image 202 (the white light image 202obtained in Step S30 of FIG. 12) that is secondly obtained in thecorrection mode, and the white light image 202 (the white light image202 obtained in Step S35 of FIG. 12) that is thirdly obtained, thismovement amount is approximately equal to the movement amount of theobservation object between Bq images, Gr images, or Rs images that areacquired before and after these images. Hence, in a case where thesemovement amounts are used, even though there is a slight movement in theobservation object of each of the Bp image, the Bq image, the Gr image,and the Rs image, the positional deviation of the observation objectbetween these images can be compensated for.

The correction information calculation unit 75 calculates the correctioninformation using the Bp image, the Bq image, the Gr image, and the Rsimage obtained by compensating for the positional deviation of theobservation object using the positional deviation compensation unit 302as described above. For this reason, the correction information can bemore accurately calculated than in a case where the positional deviationof the observation object is not compensated for. Hence, in the presentembodiment, since an error resulting from the movement of theobservation object can be reduced, the correction of the oxygensaturation observation mode becomes more accurate.

In addition, in the above third embodiment, the movement amountcalculation unit 301 calculates the movement amount using the whitelight images 202 generated by the image generation unit 73. However, themovement amount calculation unit 301 may calculate the movement amountusing images for generating the white light images 202, instead of thewhite light images 202. Specifically, since the image generation unit 73generates the white light images 202 using the Bt image, the Gt image,and the Rt image, the movement amount calculation unit 301 may calculatethe movement amount using any one or all of the Bt image, the Gt imageand the Rt image.

Fourth Embodiment

In the above third embodiment, in the correction mode, the movementamount is calculated from the plurality of white light images 202, andthe positional deviation of the observation object of the correctionimages is compensated for. Instead of this, however, a light quantityratio of the plurality of white light images 202 may be calculated, anda light quantity ratio of the correction images may be compensated forusing the calculated light quantity ratio.

In this case, as illustrated in FIG. 17, the special processing unit 63are provided with a light quantity ratio calculation unit 401 and alight quantity ratio compensation unit 402 that function in thecorrection mode. The light quantity ratio calculation unit 401sequentially acquires the white light images 202 from the imagegeneration unit 73, and calculates the light quantity ratio of the whitelight images 202. The light quantity of the images is, for example, anaverage value (hereinafter referred to as average luminance) of theluminances of all the pixels or some pixels, and the light quantityratio of the images is a ratio of the average luminances of images to becompared with each other. Hence, the light quantity ratio of theplurality of white light images 202 is a ratio of the average luminancesof the respective white light images 202.

The light quantity ratio compensation unit 402 compensates for the lightquantity ratio of the correction images using the light quantity ratiocalculated by the light quantity ratio calculation unit 401. Forexample, in a case where the light quantity ratio calculation unit 401calculates a light quantity ratio between the white light image 202 (thewhite light image 202 obtained in Step S25 of FIG. 12) that is firstobtained in the correction mode, and the white light image 202 (thewhite light image 202 obtained in Step S30 of FIG. 12) that is nextobtained, the light quantity ratio represents approximately a change inthe quantity of light between Bp images, Bq images, or Gr images thatare acquired before and after the white light images 202. Additionally,in a case where the light quantity ratio calculation unit 401 calculatesa light quantity ratio between the white light image 202 (the whitelight image 202 obtained in Step S30 of FIG. 12) that is secondlyobtained in the correction mode, and the white light image 202 (thewhite light image 202 obtained in Step S35 of FIG. 12) that is thirdlyobtained, the light quantity ratio represents approximately a change inthe quantity of light between Bq images, Gr images, or Rs images thatare acquired before and after these white light images 202. Hence, thelight quantity ratio compensation unit 402 can compensate for the lightquantity ratios of the Bp image, the Bq image, the Gr image, and the Rsimage by using these light quantity ratios.

Then, the correction information calculation unit 75 calculates thecorrection information using the Bp image the Bq image, the Gr image,and the Rs image obtained by compensating for the light quantity ratiosusing the light quantity ratio compensation unit 402, as describedabove. For this reason, even though there are changes in the quantity oflight between the Bp image, the Bq image, the Gr image, and the Rs imagebecause there are variations in light emission amount between the firstblue light BS, the second blue light BL, the green light G, and the redlight R that are the illumination light, the light quantity ratio ofthese respective correction images is compensated for. Thus, in thepresent embodiment, the correction information can be accuratelycalculated. Hence, in the present embodiment, since an error resultingfrom the changes in the quantity of light between the correction imagescan be reduced, the correction of the oxygen saturation observation modebecomes more accurate.

In addition, in the above fourth embodiment, the light quantity ratiocalculation unit 401 calculates the light quantity ratio using the whitelight images 202 generated by the image generation unit 73. However, thelight quantity ratio calculation unit 401 may calculate the lightquantity ratio using images for generating the white light images 202,instead of the white light images 202. Specifically, since the imagegeneration unit 73 generates the white light images 202 using the Btimage, the Gt image, and the Rt image, the light quantity ratiocalculation unit 401 may calculate the light quantity ratio using anyone or all of the Bt image, the Gt image and the Rt image.

In addition, the above fourth embodiment may also be combined with thethird embodiment. That is, the movement amount and the light quantityratio may be calculated from the plurality of white light images 202obtained in the correction mode, the positional deviation of theobservation object of the correction images may be compensated for usingthese, and the light quantity ratio of the correction images may becompensated for. In this case, the movement amount calculation unit 301and the positional deviation compensation unit 302 of the thirdembodiment, and the light quantity ratio calculation unit 401 and thelight quantity ratio compensation unit 402 of the fourth embodiment inthe special processing unit 63 may be provided.

Fifth Embodiment

In the correction modes of the above first to fourth embodiments, oneset of correction images (one set of the Bp image, the Bq image, the Grimage, and the Rs image) are acquired to correct the oxygen saturationobservation mode. However, in the correction modes, a plurality of setsof the correction images may be obtained. For example, as illustrated inFIG. 18, similar to the first embodiment, the first blue light BS, thewhite light, the second blue light BL, the green light G, and the redlight R may be defined as one set, and for example, a first set to afifth set can be collectively executed. Images obtained at the time ofemission of the respective lights are the same as those of the firstembodiment. Thus, in a case where the correction images only aredescribed, the Bp image, the Bq image, the Gr image, and the Rs imageare defined as one set and five sets of the correction images areobtained.

In this way, in a case where the correction images equivalent to theplurality of sets are obtained in the correction mode, a plurality ofthe compensation amounts ΔD can be calculated by using some correctionimages among these correction images and changing the combination ofcorrection images to be used. In a case where the correction imagesequivalent to the above five sets are obtained, the compensation amountcalculation unit 76 is able to use at least the correction informationcalculated using the first set of correction images, thereby calculatinga first-set compensation amount (hereinafter referred to as acompensation amount ΔD1 for the purpose of distinction; the same alsoapplies to the other sets) resulting from the first set of correctionimages. Similarly, a second-set of compensation amount ΔD2, a third-setcompensation amount ΔD3, a fourth-set compensation amount ΔD4, and afifth-set compensation amount ΔD5 may be calculated.

For example, in a case where the average value of the above compensationamounts ΔD1 to ΔD5 is set to the compensation amount ΔD of the abovefirst embodiment, an error resulting from variations or the like in datacan be reduced, and the compensation amount ΔD that is still moreaccurate than the above first embodiment can be calculated. Hence, theoxygen saturation observation mode can be more accurately corrected byobtaining the correction images equivalent to a plurality of sets in thecorrection mode as in the present embodiment.

In addition, in the above fifth embodiment, the compensation amounts ΔD1to ΔD5 are calculated for the above sets, respectively. However,compensation amounts may also be calculated by using correction imagesobtained in different sets in combinations. For example, compensationamounts ΔD may be calculated using the Bq image, the Gr image, the Rsimage that are obtained in the first set and the Bp image obtained inthe second set. Additionally, compensation amounts may be calculatedusing the Gr image and the Rs image that are obtained in the first set,and the Bp image and the Bq image that are obtained in the second set.Similarly, twelve compensation amounts ΔD in total may be calculated bychanging correction images to be used for two imaging frames. In thisway, in a case where five or more compensation amounts ΔD also includingthe compensation amounts ΔD calculated by combining the correctionimages obtained in different sets together are averaged, the averagedcompensation amount ΔD becomes a value that is still more accurate thanthat of the above fifth embodiment. Hence, as a result, the oxygensaturation observation mode can be still more accurately corrected.

Additionally, in the above fifth embodiment and modification examples,after the plurality of compensation amounts ΔD are calculated in thecorrection mode, these compensation amounts are averaged. However,instead of this averaging, a median value or the like of the pluralityof compensation amounts ΔD, may be the compensation amount ΔD to be usedby the correction unit 77.

As in the above fifth embodiment, in a case where the plurality ofcompensation amounts Δ are calculated by acquiring the correction imagesequivalent to the plurality of sets in the correction mode, asillustrated in FIG. 19, it is preferable that the special processingunit 63 is further provided with a movement amount calculation unit 511.Similar to the movement amount calculation unit 301 of the thirdembodiment, the movement amount calculation unit 511 sequentiallyacquires the white light images 202 from the image generation unit 73,and calculates the movement amounts of the observation object betweenthe plurality of acquired white light images 202. However, the movementamount calculation unit 511 inputs the calculated movement amount to thecompensation amount calculation unit 76.

Then, in the compensation amount calculation unit 76, as in the abovefifth embodiment, the plurality of compensation amounts ΔD arecalculated, and a value obtained by weighting and averaging theplurality of compensation amounts ΔD using the movement amount, is setto the compensation amount ΔD to be used in the correction unit 77. Forexample, in a case where the five compensation amounts ΔD1 to ΔD5 arecalculated for the above sets, respectively, and respective movementamounts of the first to fifth sets (or average values of the movementamounts of the respective sets) are α1 to α5, respectively, thecompensation amount calculation unit 76 multiplies the compensationamounts ΔD1 to ΔD5 of the respective sets by these movement amounts α1to α5, respectively to average the results, and calculates thecompensation amount ΔD to be used in the correction unit 77. In thisway, in a case where the correction unit 77 compensates for thecorrelation using a value obtained by performing weighting and averagingusing the movement amounts, the oxygen saturation observation mode canbe still more accurately corrected than the above fifth embodiment.

Additionally, instead of performing weighting and averaging using themovement amount as described above to average the plurality ofcompensation amounts ΔD, the compensation amount calculation unit 76 mayselect the compensation amount ΔD optimal for the correction of theoxygen saturation observation mode from the plurality of compensationamounts ΔD using the movement amount. For example, in a case where thefive compensation amounts ΔD1 to ΔD5 are calculated for the above sets,respectively, the respective movement amounts of the first to fifth sets(or average values of the movement amounts of the respective sets) areα1 to α5, respectively, and the movement amount α3 of the third setamong these movement amounts α1 to α5 is the minimum, the compensationamount calculation unit 76 selects the third-set compensation amount ΔD3as the compensation amount ΔD to be used by the correction unit 77. Inthis way, in a case where the compensation amount ΔD of a set with thesmallest movement amount or the compensation amount ΔD calculated usingthe correction images of a combination with the smallest movement amountis selected and is used for the compensation of the oxygen saturationobservation mode, the oxygen saturation observation mode can becorrected more easily than a case where the weighted averaging isperformed and more accurately than in the fifth embodiment.

As illustrated in FIG. 20, instead of the movement amount calculationunit 511, a light quantity ratio calculation unit 521, which calculatesthe light quantity ratio of the plurality of white light images 202 maybe provided similarly to the fourth embodiment. However, the lightquantity ratio calculation unit 521 calculates a plurality of lightquantity ratios, for example, for each set. In this case, the lightquantity ratios calculated by the light quantity ratio calculation unit521 may be used instead of the movement amount calculated by themovement amount calculation unit 511. That is, the plurality ofcompensation amounts ΔD may be weighted and averaged using the lightquantity ratios calculated by the light quantity ratio calculation unit521, and the compensation amount ΔD to be used in the correction unit 77may be calculated. Additionally, the compensation amount ΔD (forexample, the compensation amount ΔD of a set with a minimum lightquantity ratio) optimal for the correction of the oxygen saturationobservation mode can be selected from the plurality of compensationamounts ΔD using the light quantity ratios calculated by the lightquantity ratio calculation unit 521.

In addition, in the above fifth embodiment, how many sets of correctionimages are to be obtained during the correction mode is determined.Instead of this, however, the time to execute the correction mode may bedetermined. For example, the duration time of the correction mode may beset to 5 seconds or the like, and correction images may be acquired asmany as possible, also including the time to acquire the white lightimage 202, within this duration time.

In the above first to fifth embodiments, in a case where the observationmode is switched to the special observation mode, the correction mode isautomatically executed. However, in a case where the correction mode isnot automatically executed and the observation mode is switched to thespecial observation mode, the oxygen saturation observation mode may beautomatically executed, and the correction mode may be randomly executedduring the oxygen saturation observation mode.

For example, as illustrated in FIG. 21, the processor device 16 may beprovided with a movement amount calculation unit 611 that sequentiallyacquires oxygen saturation images to calculate the movement amount, anda determination unit 612 that determines whether or not the correctionmode is to be executed using the movement amount calculated by themovement amount calculation unit 611. For example, in a case where themovement amount becomes equal to or less than a threshold value and themovement of the observation object is small, the determination unit 612determines that the correction mode is executed, and inputting a controlsignal showing that effect to the control unit 52, thereby automaticallyinserting the correction mode during the oxygen saturation observationmode. In this way, in a case where a situation optimal for thecorrection of the oxygen saturation observation mode is determined usingthe movement amount, and the correction mode is executed in a case wherethe situation optimal for the correction of the correction mode isbrought about, the correction of the oxygen saturation observation modeis apt to succeed.

Although the movement amount calculation unit 611 calculates themovement amount from the oxygen saturation images, the movement amountmay be calculated using the images (the B1 image, the B2 image, the G2image, and the R2 image) for generating the oxygen saturation imagesinstead of the oxygen saturation images. Additionally, in a case whereit is determined that the correction mode is executed, the determinationunit 612 inputs a control signal to the control unit 52, therebyautomatically inserting the correction mode during the oxygen saturationobservation mode. Instead of this, however, the fact that the situationis suitable for the correction mode may be notified of using the display(message or the like) of the monitor 18 or the like, and manualswitching to the correction mode may be prompted. Additionally, themovement amount calculation unit 611 and the determination unit 612 maybe provided at the special processing unit 63.

As illustrated in FIG. 22, in a case where the special processing unit63 is provided with a mucous membrane determination unit 621 thatdetermines the state of a mucous membrane, the correction mode may beinserted during the oxygen saturation observation mode, in accordancewith a determination result of the mucous membrane determination unit621. The mucous membrane determination unit 621, for example, acquiresthe B1 image, the B2 image, the G2 image, or the R2 image from the imageacquisition unit 54, and detects the state of the mucous membrane of theobservation object using any one or all of these images. Then, in a casewhere there is no mutation shape or mutation structure, such asprotuberances suspected of a lesion, it is determined that the mucousmembrane of the observation object is in a state suitable for thecorrection mode, and a control signal prompting the execution of thecorrection mode is input to the control unit 52. Accordingly, thecorrection mode may be automatically inserted during the oxygensaturation observation mode.

The mucous membrane determination unit 621 may determine the color ofthe mucous membrane. For example, in a case where there is nodiscoloration (for example, redness) or the like suspected of a lesion,or in a case where the color of the mucous membrane varies due to theendoscope 12 entering the stomach from the esophagus, or the like, andit is determined that the observation object becomes a different organ,the mucous membrane determination unit 621 is able to input a controlsignal prompting the execution of the correction mode to the controlunit 52, and automatically insert the correction mode during the oxygensaturation observation mode. In addition, also in a case where themucous membrane determination unit 621 is provided, instead ofautomatically inserting the correction mode, the fact that the situationis suitable for the correction mode may be notified of using the display(message or the like) of the monitor 18 or the like, and manualswitching to the correction mode may be prompted.

In the above first to fifth embodiments, the first blue light BS, thesecond blue light BL, the green light G, and the red light R arerespectively and singly emitted in the correction mode to obtain thecorrection images. However, some lights may be simultaneously emitted orsome correction images may be simultaneously acquired. For example, asillustrated in FIG. 23, the green light G and the red light R may besimultaneously emitted, and the Gr image and the Rs image may besimultaneously acquired. Additionally, as illustrated in FIG. 24, thefirst blue light BS, the green light G, and the red light R may besimultaneously emitted to simultaneously acquire the Bp image, the Grimage, and the Rs image, and the second blue light BL may be singlyemitted to separately acquire the Bq image. Similarly, the first bluelight BS may be singly emitted to acquire the Bp image, and the secondblue light BL, the green light G, and the red light R may besimultaneously emitted to simultaneously acquire the Bq image, the Grimage, and the Rs image. That is, in a case where the first blue lightBS and the second blue light BL to be received in the B pixel arerespectively emitted in different imaging frames to separately obtainthe Bp image and the Bq image, the other correction images may besimultaneously obtained.

In the above first to fifth embodiments, basically, the oxygensaturation observation mode is corrected in a one-time correction mode.However, in a case where the correction mode is manually orautomatically executed two or more times, correction results in apreviously executed correction mode may be overlappingly corrected. Thatis, in a case where the correction mode is executed two or more times,the default correlation always stored in advance in the data storageunit 71 may not be compensated for, but a correlation that iscompensated for in the previous correction mode may be compensated for.By doing in this way, even though the correction accuracy in theone-time correction mode is somewhat low, the correction accuracy can beimproved stepwise.

In the above first to fifth embodiments, the biological informationobservation mode is the oxygen saturation observation mode. However, theinvention can also be applied to the biological information observationmode in which biological information other than the oxygen saturation iscalculated and the like.

In the above first to fifth embodiments, the plurality of correctionillumination lights having different colors (wavelength) are used in thecorrection mode. However, the correction of the biological informationobservation mode may be performed using a plurality of preliminarilycaptured images obtained by imaging the observation object two or moretimes using correction illumination lights having the same color.

In the above first to fifth embodiments, the light source unit 20 hasthe plurality of light sources 20 a to 20 d, and lights emitted by theselight sources are overlapped with each other to form the illuminationlight. However, the light source unit 20 may form the illumination lightby extracting and using some components from the light emitted by abroadband light source. For example, in an endoscope system 670illustrated in FIG. 25, the light source unit 20 is provided with abroadband light source 676, a rotation filter 677, and a filterswitching unit 678 instead of the respective light sources 20 a to 20 dand the light source control unit 22 of the first embodiment.Additionally, in the endoscope system 670, the image sensor 48 is amonochrome sensor in which the color filter is not provided. The othersare the same as those of the endoscope system of the first embodiment.

The broadband light source 676 is a xenon lamp, a white LED, or thelike, and emits the white light of which the wavelength range rangesfrom blue to red. The rotation filter 677 is rotatably disposed on alight path of the broadband light source 676, limits the range of thewhite light emitted by the broadband light source 676, and somecomponents of the white light are incident on the light guide 41 as theillumination light.

As illustrated in FIG. 26, the rotation filter 677 is circular and hasband limiting filters, respectively, at an inner periphery and an outerperiphery thereof. A band limiting filter (hereinafter referred to as aninner filter) 688 at the inner periphery are divided into fourcompartments in the circumferential direction, and each compartment isprovided with a BS filter 688 a through which the first blue light BS istransmitted, a G filter 688 b through which the green light G istransmitted, and an R filter 688 c through which the red light R istransmitted. A band limiting filter (hereinafter referred to as an outerfilter) 689 at the outer periphery are divided into five compartments inthe circumferential direction, and each compartment is provided with aBS filter 689 a through which the first blue light is transmitted, a BLfilter 689 b through which the second blue light BL is transmitted, a Gfilter 689 c through which the green light G is transmitted, an R filter689 d through which the red light R is transmitted, a W filter 689 ethrough which the white light is transmitted.

The filter switching unit 678 switches the position of the rotationfilter 677 to the light path of the broadband light source 676 inaccordance with a control signal input by the control unit 52 and inaccordance with the observation modes. Additionally, the filterswitching unit 678 also adjusts the rotating speed of the rotationfilter 677 in accordance with the observation modes. In the case of thenormal observation mode, the filter switching unit 678 disposes theinner filter 688 on the light path of the broadband light source 676,and rotates the rotation filter 677 in accordance with to the imagingframes. The Bc image can be obtained in an imaging frame in which the BSfilter 688 a passes through the light path of the broadband light source676. Similarly, the Gc image can be obtained in an imaging frame inwhich the G filter 688 b passes through the light path of the broadbandlight source 676, and the Rc image can be obtained in an imaging framein which the R filter 688 c passes through the light path of thebroadband light source 676.

Meanwhile, in the case of the special observation mode, the filterswitching unit 678 disposes the outer filter 689 on the light path ofthe broadband light source 676, and rotates the rotation filter 677 inaccordance with to the imaging frames. Accordingly, in the correctionmode, in the respective imaging frames in which the respective filters689 a to 689 e of the outer filter 689 pass the light path of thebroadband light source 676, the Bp image, the Bq image, the Gr image,the Rs image, and the white light images 202 can be obtained.Additionally, in the oxygen saturation observation mode, the B1 image,the B2 image, the G2 image, and the R2 image can be obtained,respectively, in the respective imaging frames in which the BS filter689 a, the BL filter 689 b, the R filter 689 c, and the R filter 689 dof the outer filter 689 pass through the light path of the broadbandlight source 676.

The above configuration of the rotation filter 677 is an example. Forexample, in a case where the compartment for the W filter 689 e of theouter filter 689 is increased, and W filters 689 e are also respectivelydisposed between the BS filter 689 a and the BL filter 689 b, betweenthe BL filter 689 b and the G filter 689 c, and between the G filter 689c and the R filter 689 d, the white light images 202 can be obtained inimaging frames during, before, or after the respective correctionimages, similarly to the first embodiment, in the correction mode. Inaddition, in a case where the image generation unit 73 generates thewhite light images 202 from the Bq image, the Gr image, and the Rsimage, the W filter 689 e may also be omitted. Additionally, the outerfilter 689 may be further divided at the inner and outer peripheries,and a portion for the correction mode and a portion for the oxygensaturation observation modes may be provided.

In addition, in the above first to fifth embodiments, the invention iscarried out in the endoscope system that performs observation byinserting the endoscope 12 provided with the image sensor 48 into asubject. However, the invention is also suitable for a capsule endoscopesystem. As illustrated in FIG. 27, for example, the capsule endoscopesystem has at least a capsule endoscope 700 and a processor device (notillustrated).

The capsule endoscope 700 includes a light source unit 702, a controlunit 703, an image sensor 704, an image processing unit 706, and atransmission/reception antenna 708. The light source unit 702corresponds to the light source unit 20. The control unit 703 functionssimilarly to the light source control unit 22 and the control unit 52.Additionally, the control unit 703 is capable of wirelesslycommunicating with the processor device of the capsule endoscope systemusing the transmission/reception antenna 708. Although the processordevice of the capsule endoscope system is substantially the same as thatof the above processor device 16 of the first to fifth embodiments, theimage processing unit 706 corresponding to the image acquisition unit 54and the image processing unit 61 is provided in the capsule endoscope700, and a generated oxygen saturation image or the like is transmittedto the processor device via the transmission/reception antenna 708. Theimage sensor 704 is configured similarly to the image sensor 48.

EXPLANATION OF REFERENCES

-   -   10, 670: endoscope system    -   12: endoscope    -   12 a: insertion part    -   12 b: operating part    -   12 c: bending part    -   12 d: distal end part    -   12 e: angle knob    -   13 a: switch    -   13 b: zooming operation part    -   14: light source device    -   16: processor device    -   18: monitor    -   19: console    -   20, 702: light source unit    -   20 a: BS light source    -   20 b: BL light source    -   20 c: G light source    -   20 d: R light source    -   22: light source control unit    -   30 a: illumination optical system    -   30 b: imaging optical system    -   41: light guide    -   45: illumination lens    -   46: objective lens    -   47: zoom lens    -   48, 704: image sensor    -   52, 703: control unit    -   54: image acquisition unit    -   56: DSP    -   58: noise reduction unit    -   59: converting unit    -   61, 706: image processing unit    -   62: normal processing unit    -   63: special processing unit    -   66: display control unit    -   70: arithmetic value calculation unit    -   71: data storage unit    -   72: biological information calculation unit    -   73: image generation unit    -   75: correction information calculation unit    -   76: compensation amount calculation unit    -   77: correction unit    -   83: isoplethic line    -   84: isoplethic line    -   86, 87: graph    -   94: referential equal concentration line    -   96: equal concentration line    -   201: region setting unit    -   202: white light image    -   203: use region    -   301, 511, 611: movement amount calculation unit    -   302: positional deviation compensation unit    -   401, 521: light quantity ratio calculation unit    -   402: light quantity ratio compensation unit    -   612: determination unit    -   621: mucous membrane determination unit    -   676: broadband light source    -   677: rotation filter    -   678: filter switching unit    -   688, 689: band limiting filter    -   688 a, 689 a: BS filter    -   688 b, 689 c: G filter    -   688 c, 689 d: R filter    -   689 b: BL filter    -   689 e: W filter    -   700: capsule endoscope    -   708: transmission/reception antenna

What is claimed is:
 1. An endoscope system having a biologicalinformation observation mode in which biological information on anobservation object is observed, and a correction mode in which thebiological information observation mode is corrected, the endoscopesystem comprising: a light source unit that includes a first blue lightsource, a green light source, a red light source, and a second bluelight source, the first blue light source emitting first blue light, thegreen light source emitting green light, the red light source emittingred light, and the second blue light source emitting second blue lighthaving a longer central wavelength than a central wavelength of thefirst blue light; wherein the light source unit emits the second bluelight in the biological information observation mode, and sequentiallyemits the green light and a white light in the correction mode, theendoscope system further comprising a processor configured to: calculatea compensation amount using a correction image having a biologicalinformation obtained by imaging the observation object using the greenlight; correct a correlation to be used in the biological informationobservation mode using the compensation amount; calculate, according tothe corrected correlation, biological information based on an imageobtained by imaging the observation object using the second blue light;and display a white light image which is obtained by imaging theobservation object using the white light, on a display unit in thecorrection mode, wherein at least the first blue light source, the greenlight source, and the red light source are configured to be turned onsimultaneously to emit the white light.
 2. The endoscope systemaccording to claim 1, wherein the biological information is an oxygensaturation of the observation object.
 3. The endoscope system accordingto claim 2, wherein the second blue light source emits the second bluelight having a central wavelength of 470 nm±10 nm.
 4. The endoscopesystem according to claim 3, wherein the correction image is one of aplurality of correction images, the white light image is one of aplurality of white light images, in the correction mode, the pluralityof the correction images are acquired, and the plurality of the whitelight images are acquired.
 5. The endoscope system according to claim 4,wherein the processor is configured to: set a portion of each of thecorrection images to a region to be used for the correction of thebiological information observation mode; and overlappingly display theregion set on the white light image.
 6. The endoscope system accordingto claim 5, wherein the processor is configured to: calculate a movementamount of the observation object; calculate a plurality of compensationamounts by using some correction images among the plurality ofcorrection images; and select compensation amount optimal for thecorrection of the biological information observation mode from theplurality of compensation amounts using the movement amount.